The present invention is directed to a method for injecting fuel into the cylinders of a multi-cylinder internal-combustion engine.
In a four-cycle internal combustion engine, the crankshaft can cover an angle of 720.degree. dependent on a working cycle, i.e., it executes two full revolutions before a specific cylinder returns to the same working position, for example, at the next ignition time. In order to acquire a momentary position of a cylinder, it is not adequate to identify the angular position of the crankshaft within only a full revolution. Additional information is needed as to whether the engine is currently in a first half or in a second half of the operating cycle, corresponding to the first or second crankshaft revolution.
To that end, it is known in the prior art to provide a static position transmitter whose periodic position signal is composed of two sub-signals, an A-signal and a B-signal that each alternately extend over a full crankshaft revolution. A position transmitter additionally supplies a position signal with a reference pulse per revolution of the crankshaft from which a known angular position, the synchronization position, is identified. In combination with the position signal, the position of the cylinder of the internal-combustion engine can be known precisely only with the detection of the reference pulse and a synchronization of electrical control functions, such as ignition, injection, etc., and the synchronization of the cylinder positions.
After the start of the internal-combustion engine a full crankshaft revolution can pass in the worst case before the synchronization position is reached for the first time. Only then can fuel be injected into the individual cylinders in a proper cycle.
In order to avoid a lengthening of the starting phase due to the absence of fuel injection during the first crankshaft revolution, it is known to simultaneously inject fuel into all cylinders immediately upon starting, this is referred to as bank injection. Dependent on the position of the crankshaft when starting, however, this leads to a double injection into some cylinders after the synchronization time and after the transition to normal injection. Moreover for at least one cylinder, the fuel is injected into the open intake valve, as a consequence whereof an additional increase in the exhaust emission results.